1. Field of the Invention
This invention relates to a circuit for controlling the brightness of a light emitting indicator, and more particularly to an electric control circuit which controls the brightness of an indicator consisting of light emitting diodes provided in the field of view of a viewfinder of a photographic camera for indicating exposure information.
2. Description of the Prior Art
In the conventional photographic cameras, it has been known to indicate exposure information such as shutter speed or aperture size which is automatically controlled by an exposure control circuit provided in the camera. The exposure information is indicated by an indicator consisting of light emitting diodes provided in the field of view of the viewfinder of the camera. Since the viewfinder is used to view the scene to be photographed, the brightness of the indicator is desired to be changed as the brightness of the scene is changed. If the brightness of the indicator is too high when the scene brightness is low, the scene is hard to see because of the halation caused by the bright indicator. To the contrary, if the brightness of the indicator is low when the scene brightness is very high for instance in case of shooting an object in the snowy scene, the indicator becomes hard to see.
Further, in the conventional photographic camera with an exposure control circuit, there is provided a photoreceptor for measuring the scene brightness in the viewfinder optical system. The photoreceptor provided in the viewfinder system receives to some extent the light emitted by the indicator in the viewfinder system. The amount of the light from the indicator received by the photoreceptor will cause an error in the exposure control. Therefore, from this viewpoint also, it is desirable that the brightness of the indicator should be lowered when the brightness of the scene is low.